Due to the difference of the retardation caused by different angles of light passing through a liquid crystal layer of a liquid crystal display, the light transmittance of a liquid crystal display when viewing from the front is different from the light transmittance of the liquid crystal display when viewing from the side. Hence, the refractive index of the light will change according to different observation angles and result in different transmittance and different brightness when viewing from different angles. Additionally, a color distortion phenomenon will result when different colors of light (such as red light, green light, and blue light) are combined at different brightness.
FIG. 1 shows an arrangement of subpixels of a color display 10 according to the prior art that attempts to address some of the issues noted above. As shown in FIG. 1, a conventional color display 10 (such as a liquid crystal display) includes a plurality of pixel groups 11 and 12, in which the pixel groups are arranged in a matrix. Each pixel group includes a red pixel, a green pixel, and a blue pixel. Taking pixel group 11 as an example, the red pixel includes a red first subpixel 111 and a red second subpixel 112, the green pixel includes a green third subpixel 113 and a green fourth subpixel 114, and the blue pixel includes a blue fifth subpixel 115 and a blue sixth subpixel 116.
The two subpixels of each color pixel are driven by bright state signals and dark state signals, such that the subpixels will combine to form a gray scale value and display a color, thereby improving the overall viewing angle of the display and color distortion generated during larger viewing angles. As shown in FIG. 2, the red first subpixel 111 is driven by a bright state red (R1) display signal and the red second subpixel 112 is driven by a dark state red (R1) display signal (slanted lines shown in FIG. 2 indicate that they are driven by a dark state display signal). The red first subpixel 111 and the red second subpixel 112 combine to form the red color (R1) of the first pixel group 11 for improving the color distortion and viewing angle of the red color of pixel group 11. Similarly, the green pixel and the blue pixel within the first pixel group 11 are driven by the same method to improve the color distortion and viewing angle of the first pixel group 11.
At the same gray scale value, each color will produce a color distortion due to different front view normalized transmittance and side view normalized transmittance. Additionally, when the gray scale value approaches 0 or 255, the difference between the front view normalized transmittance and the side view normalized transmittance will decrease and approaches 0%. This feature of small or zero difference between front view normalized transmittance and side view normalized transmittance as gray scale values approach 0 and 255 can be used in conjunction with the arrangement of FIG. 1 and the bright state/dark state signal driving technique of FIG. 2 to achieve less color distortion at different viewing angles. For example, using the arrangement of FIGS. 1 and 2, to achieve an original gray scale value of 128 for the blue pixel, a dark state signal (such as a dark state gray scale value) can be selected to be zero, and a bright state signal (such as a bright state gray scale value) can be selected to be 190, such that the signals are utilized as a group of calibrating gray scale values (including the dark state gray scale value and the bright state gray scale value stated above) to obtain the original gray scale value, in which the difference between the front view normalized transmittance and the side view normalized transmittance of the calibrating gray scale values is less than the difference between the front view normalized transmittance and the side view normalized transmittance of the original gray scale value 128. Consequently, the users are able to perceive equal brightness as the original gray scale value while viewing the liquid crystal display from the front and from the side and at the same time, improve problems such as color distortion by utilizing the calibrated gray scale values.
Nevertheless, since the subpixels driven by the bright state signal are collectively gathered in the first row and the subpixels driven by the dark state signal are gathered in the second row of respective pixel groups in FIG. 2, a resultant uneven brightness phenomenon may still result in a negative viewing effect.